Wrote Letter L-058 of 1677-10-05 to Henry Oldenburg about skin, eels, fleas, and measuring and counting the little animals; enclosed testimonials

October 5, 1677
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Leeuwenhoek's number: 
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Text of the letter in the original Dutch and in English translation from Alle de Brieven. The Collected Letters at the DBNL - De Digitale Bibliotheek voor de Nederlandse Letteren

The original manuscript on eight folio pages, written and signed by Leeuwenhoek, is preserved at the Royal Society (MS. 1858. Early Letters L1.29). A Latin translation is Early Letters L1.30. The original manuscripts of the five testimonal letters are also found at Early Letters L1.30.

Leeuwenhoek wrote this letter, sent with a Latin translation, to Henry Oldenburg (who had died a month earlier in September) in reply to Oldenburg's Letter L-057 of 7 August 1677 (28 July O.S.). Leeuwenhoek wrote about:

  • his theory for the existence of different skin colours
  • the reproduction of eels and their blood; the reproduction of lice
  • comparison of the larvae of fleas with silk-worms; discussed Swammerdam's views on fleas
  • his demonstration of a grain of millet as a measure of cubic capacity and states that he sends 8 testimonials about this (inserted after EL/L1/30);
  • numbers of organisms living in a drop of water.

Hooke published the second half of letter in Microscopium in early 1678, followed by a short discussion of Hooke's own efforts at lensmaking.

Leeuwenhoek enclosed five letters with the testimony of eight credible eye-witnesses to microorganisms in infusions.

J. Boogert, lawyer and notary in Delft
W. van der Burch
Hendrik Cordes, Lutheran minister in Den Haag
Robbert Gordon, medical student in Leiden
Benedictus Haan, Lutheran minister in Delft
Aldert Hodenpijl, manager of the Comanscolff, the St. Nicolaas guildhouse (of which Leeuwenhoek was a member) on the Oude Langendijk in Delft
Alexander Petrie, minister of the Scottish church in Rotterdam
Robert Poitevin, doctor of medicine

Volume 2 of Alle de Brieven / Collected Letters (p 449), probably following Dobell (p. 176), misidentifies the Leiden medical student as English baronet Sir Robert Gordon (1647-1704).

In 1694, Beneditcus Haan, by then living in Amsterdam, wrote another letter in support of Leeuwenhoek's observations.